1. Field of the Invention
The invention relates to implant devices that may be implanted in an atrial appendage for filtering blood flowing between the atrial appendage and an associated atrium of the heart to prevent thrombi from escaping from the atrial appendage into the body's blood circulation system.
2. Description of the Related Art
There are a number of heart diseases (e.g., coronary artery disease, mitral valve disease) that have various adverse effects on a patient's heart. An adverse effect of certain cardiac diseases, such as mitral valve disease, is atrial (or auricular) fibrillation. Atrial fibrillation leads to depressed cardiac output. A high incidence of thromboembolic (i.e., blood clot particulate) phenomena are associated with atrial fibrillation, and the left atrial appendage (LAA) is frequently the source of the emboli (particulates).
Thrombi (i.e., blood clots) formation in the LAA may be due to stasis within the fibrillating and inadequately emptying LAA. Blood pooling in the atrial appendage is conducive to the formation blood clots. Blood clots may accumulate, build upon themselves. Small or large fragments of the blood clots may break off and propagate out from the atrial appendage into the atrium. The blood clot fragments can then enter the body's blood circulation and embolize distally into the blood stream.
Serious medical problems result from the migration of blood clot fragments from the atrial appendage into the body's blood stream. Blood from the left atrium and ventricle circulates to the heart muscle, the brain, and other body organs, supplying them with necessary oxygen and other nutrients. Emboli generated by blood clots formed in the left atrial appendage may block the arteries through which blood flows to a body organ. The blockage deprives the organ tissues of their normal blood flow and oxygen supply (ischemia), and depending on the body organ involved leads to ischemic events such as heart attacks (heart muscle ischemia) and strokes (brain tissue ischemia).
It is therefore important to find a means of preventing blood clots from forming in the left atrial appendage. It is also important to find a means to prevent fragments or emboli generated by any blood clots that may have formed in the atrial appendages, from propagating through the blood stream to the heart muscle, brain or other body organs.
U.S. Pat. No. 5,865,791 (hereinafter, “the '791 patent”) relates to the reduction of regions of blood stasis in the heart and ultimately reduction of thrombi formation in such regions, particularly in the atrial appendages of patients with atrial fibrillation. More specifically, the '791 patent relates to procedures and devices for affixing the atrial appendages in an orientation that prevents subsequent formation of thrombi. In the '791 patent, the appendage is removed from the atrium by pulling the appendage, placing a loop around the appendage to form a sack, and then cutting it off from the rest of the heart.
U.S. Pat. No. 5,306,234 describes a method for surgically closing the passage way between the atrium and the atrial appendage, or alternatively severing the atrial appendage.
Some recently proposed methods of treatment are directed toward implanting a plug-type device in an atrial appendage to occlude the flow of blood therefrom.
A preventive treatment method for avoiding thromboembolic events (e.g., heart attacks, strokes, and other ischemic events) involves filtering out harmful emboli from the blood flowing out of atrial appendages. Co-pending and co-owned U.S. patent application Ser. No. 09/428,008, U.S. patent application Ser. No. 09/614,091, U.S. patent application Ser. No. 09/642,291, and U.S. patent application Ser. No. 09/697,628, all of which are hereby incorporated by reference in their entireties herein, describe filtering devices which may be implanted in an atrial appendage to filter the blood flow therefrom. The devices may be delivered to the atrial appendage using common cardiac catheterization methods. These methods may include trans septal catheterization which involves puncturing an atrial septum.
Catheters and implant devices that are large may require large punctures in the septum. Large catheters and devices may damage body tissue during delivery or implantation. Damage to body tissue may cause trauma, increase recovery time, increase the risk of complications, and increase the cost of patient care. Further the atrial appendages may vary in shape and size from patient to patient.
It would therefore be desirable to provide implant devices which are small and which can be delivered by small-sized catheters to the atrial appendages. It would therefore also be desirable to provide implant devices whose size can be adjusted in situ to conform to the size of the atrial appendages.